There are numerous system applications and particularly modern microwave systems which require narrowband perfection with broadband versatility. In U.S. Pat. No. 4,063,176, assigned to the assignee of the present invention, there is shown and described a broadband mixer using tapered ground plane microstrip transmission line baluns. The present invention discloses other forms of novel transmission line baluns and a mixer using these baluns also having extremely good performance characteristics that are usable in many system applications including airborne and marine ECM and communications equipment, satellite earth station transmitters and receivers, overland microwave communication links, as well as phase-locked sources, broadband sweepers, and heterodyne frequency counters.
Accordingly, it is an object of the present invention to provide novel and improved ultra-high bandwidth transmission line baluns.
Another object of the present invention is to provide high performance, relatively small size, lightweight, durable transmission line baluns that are usable in a variety of modern system applications.
Yet another object of the present invention is to provide a double slot balun characterized by an extremely wide frequency response, adjustable impedance transformation, a low voltage standing wave ratio and electromagnetic field distribution in a substantially planar direction.
Still another object of the present invention is to provide a double slot balun principally characterized by two separate pairs of coplanar conductive sheets in a spaced, superposed and electrically insulated relation to one another to form two slots in a spaced, parallel relation with parallel conductive sheets having the same polarities when alternating electric energy is applied to one end of the slots.
A further object of the present invention is to provide a constant impedance balun characterized by an extremely wide bandwidth, a one-to-one impedance transformation, low voltage standing wave ratios, and good performance down to the frequency corresponding to the one-eighth wavelength point.
Yet a further object of the present invention is to provide a constant impedance transmission line balun principally characterized by two alined, spaced, parallel conductive strips electrically insulated from one another with one conductive strip tapered with a selected taper and the other conductive strip adjusted relative to the selected taper to provide a constant impedance at any point along the conductive strips taken at any cross section that is perpendicular to the center lines of the two conductive strips.
Still a further object of the present invention is to provide a novel broadband mixer using transmission line baluns that has extremely wide bandwith characteristics, low conversion losses, low voltage standing wave ratios, and good isolation between ports.